Nato Secretary General Jens Stoltenberg has warned US President-elect Donald Trump that "going it alone" is not an option for Europe or the United States.
He said the West faced its greatest security challenge in a generation.
During his election campaign, Mr Trump described Western military alliance Nato as obsolete.
He suggested that the US would think twice about coming to the aid of any Nato ally under attack if it had not paid its dues.
Writing in Britain's Observer newspaper, Mr Stoltenberg conceded that Mr Trump had a point about the need for some members to make a bigger financial contribution, as the US currently accounted for almost 70% of Nato spending.
But he added that American leaders had always recognised that they had a profound strategic interest in...Read more...